Questions tagged [attack]

Relates to attempts to harm the Bitcoin network. In cryptography, an attack is a method/technique to break the code. Bitcoin also has to deal with other types of attack, such as double spends and denial of service.

If a malicious miner changes the amount in a given transaction, the hash value of the block changes. Thus, he has to find the required hash value again in that block. Let's say he successfully found ...

I have just read about sidechains in Bitcoin here. When I want to transfer coins between chains, I have to wait for a 1-2 day confirmation period. According to above source, the confirmation period is ...

I am trying to set up a new Bitcoin full node and my institution ISP is trying hard to not give me a static IP address for this purpose. I guess because of the concern that the node will be DDoSed, ...

I was wondering if we where to ever face a 51% attack is there some sort of limit as to when the longest chain doesn't matter? For example if I owned 51%+ of the network, mined 1000 blocks privately ...

Consider in a block-withholding attack (aka selfish mining attack), attacker after creating a new block decides to broadcast this new block only to a fraction of network, such that eventually only a ...

Upon receiving a newly mined block, the block timestamp validation is performed here:
https://github.com/bitcoin/bitcoin/blob/master/src/validation.cpp#L3263-L3270
Q1: As for the second check (block ...

Okay, so, here is my scenario:
Imagine a group of miners who are mining a coin are responsible for a large portion of the hash rate on the network (let's say not quite 50%). Looking at the parameters ...

In a typical case of finding a collision with an address, as long as the private key provided has a consistent public key that hashes to the address, then the coins in that address can be spent. The ...

Let's imagine, an attacker managed to corrupt your local list of unspent transaction outputs (or a blockhain explorer you use) in a way that certain unspent transaction outputs seem to hold less coins ...

I have deployed several altcoins using various PoW algorithms on my LAN for my buddies and I to mine/learn from. We ultimately want to go the distance of deploying an altcoin to the world, writing the ...

Say I want to break a Litecoin private key having the public key using brute force. How much computing power is required for that? Does any hardware exist which can find a matching private key in, say,...

Suppose Alice wants to add a fake transaction where she receives X ammount of BTC. I understand that in order to add that transaction to the blockchain she would have to compete against all the other ...

Checkpoints prevented an attack where a node could mine many many low-difficulty blocks from an early point in the blockchain and serve those blocks to syncing nodes who would see their disks fill up. ...

I am trying to understand the recent time warp attack on verge but since the attack is universal across all POW block chain i figure I could also ask here since people here are .. more knowledgeable.
...

I've read that checkpoints in Bitcoin were removed because they were not preventing any meaningful attack.
Why should a regular checkpoint not prevent majority attacks? For instance, if a checkpoint ...

Imagine the following scenario:
I send you 1000 BTC.
After 6 confirmations, you give me what I bought.
I create another transaction with 900 BTC to my own wallet and 100 BTC as transaction fee, using ...

There is an almost trivial double-spending attack against Bitcoin if an attacker has a MITM (man-in-the-middle) attack against a victim: the attacker prevents all blocks from being seen, and replaces ...

I came to believe that an ISP can easily detect full nodes, BTC connections and isolate them from reaching any other nodes.
When and if an ISP decided to do so, could they easily perform a 51% attack ...

TL;DR: With only 30% of network power a Majority Attack is possible and profitable. Am I missing anything?
Generally speaking, blockchains based on Proof-of-Work authentications are using amount of ...

I think this question is just a re-formulation of the 51% attack, but it has me thinking: miners are monetarily incentivized to not perform a 51% attack, but there must be some amount of money will ...

This isn't a problem today, because if I want to run a pruned node then I still have to download the whole chain, but it sure would be nice if I could just download a pruned chain instead and validate ...

Im just reading a book on the basics of blockchain and I encountered a confusion regarding the 51% attack. If I'm right, it says that an attacker holding 51% or more of the network's computing power ...

Since the existence of BCH, miners can now switch chains to mine on. Assuming they mine greedily based on price and difficulty. Can the following attack happen and how could it be mitigated:
Assuming ...

I understand that proof of work prevents a node from creating a new version of the blockchain unless they have >50% of the hash rate, but what if the attacker is also able to intercept the victim's ...

There are some rules, called consensus rules. For example, block generation fee amount.
And it is said that "change to consensus rules is hard-fork".
But how exactly the consensus rules are forced?
...

I'm learning how the blockchain works. I've read that when someone (say Alice) send twice a transaction to two different peoples (Bob and Charlie) such that Alice has only enough to pay Bob or Charlie,...